Sorry - I have been a big vague!
I did say 'API' in the first posting, then 'language' in the second!
You can do Functional Programming style
in C - it's a bit of a trick, but possible. That plus a high-level gaming API such as in Raylib, can give what I want.
But I also have a proper
Functional Programming language - that is interpreted in the Java code I wrote. It would indeed, also be interpreted in the C implementation.
Sorry for the confusion.
My problem with these languages is that when it comes down to it, the new language is abandoned and a traditional language chosen instead - to do the real work.
Yup - so I'd have both an API with everything high level, plus the new language, and hope that my language takes over the world and all that.
OK perhaps bootstrap it in C because C is always available, but then write the interpreter in the new language.
If the new language is incapable of the task, or too slow, then perhaps its a bad choice.
The new language interpreter is written in C.
I don't think I'm explaining this too well - or did I?